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129 lines
3.0 KiB
129 lines
3.0 KiB
6 years ago
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/*
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* =============================================================
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* pagerank_mult.c Compute the matrix vector multiplication
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* between the PageRank matrix and a vector
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*
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* David Gleich
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* Stanford University
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* 14 February 2006
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* =============================================================
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*/
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#include "mex.h"
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/*
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* The mex function just computes one matrix-vector product.
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*
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* function y = pagerank_mult(x,Pt,c,d,v)
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* y = c*Pt*x + (c*(d'*x))*v + (1-c)*sum(x)*v;
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*/
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void mexFunction(int nlhs, mxArray *plhs[],
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int nrhs, const mxArray *prhs[])
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{
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int i, j, k;
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int n, mrows, ncols;
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/* sparse matrix */
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int *A_row, *A_col;
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double *A_val;
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double *x, *d, *v;
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double c;
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double *y;
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double sum_x;
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double dtx;
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double xval;
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if (nrhs != 5)
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{
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mexErrMsgTxt("5 inputs required.");
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}
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else if (nlhs > 1)
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{
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mexErrMsgTxt("Too many output arguments");
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}
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mrows = mxGetM(prhs[1]);
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ncols = mxGetN(prhs[1]);
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if (mrows != ncols ||
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!mxIsSparse(prhs[1]) ||
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!mxIsDouble(prhs[1]) ||
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mxIsComplex(prhs[1]))
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{
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mexErrMsgTxt("Input must be a noncomplex square sparse matrix.");
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}
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/* okay, the second input passes */
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n = mrows;
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/* The first input must be a vector. */
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if (mxGetM(prhs[0])*mxGetN(prhs[0]) != n ||
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mxIsSparse(prhs[0]) || !mxIsDouble(prhs[0]))
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{
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mexErrMsgTxt("Invalid vector 1.");
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}
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/* The third input must be a scalar. */
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if (mxGetM(prhs[2])*mxGetN(prhs[2]) != 1 || !mxIsDouble(prhs[0]))
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{
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mxErrMsgTxt("Invalid scalar 3.");
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}
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/* The fourth input must be a scalar. */
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if (mxGetM(prhs[3])*mxGetN(prhs[3]) != n ||
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mxIsSparse(prhs[3]) || !mxIsDouble(prhs[3]))
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{
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mexErrMsgTxt("Invalid vector 4.");
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}
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/* The fifth input must be a scalar. */
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if (mxGetM(prhs[4])*mxGetN(prhs[4]) != n ||
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mxIsSparse(prhs[4]) || !mxIsDouble(prhs[4]))
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{
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mexErrMsgTxt("Invalid vector 5.");
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}
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/* Get the sparse matrix */
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A_val = mxGetPr(prhs[1]);
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A_row = mxGetIr(prhs[1]);
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A_col = mxGetJc(prhs[1]);
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/* Get the vector x */
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x = mxGetPr(prhs[0]);
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/* Get the vector d */
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d = mxGetPr(prhs[3]);
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/* Get the vector v */
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v = mxGetPr(prhs[4]);
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c = mxGetScalar(prhs[2]);
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plhs[0] = mxCreateDoubleMatrix(n,1,mxREAL);
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y = mxGetPr(plhs[0]);
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sum_x = 0.0;
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dtx = 0.0;
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for (i = 0; i < n; i++)
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{
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xval = x[i];
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sum_x += xval;
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dtx += d[i]*xval;
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for (j = A_col[i]; j < A_col[i+1]; ++j)
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{
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y[A_row[j]] += c*A_val[j]*xval;
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}
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}
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xval = c*dtx + (1-c)*sum_x;
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for (i=0; i < n;i++)
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{
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y[i] += xval*v[i];
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}
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}
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